1. Field of the Invention
The present invention relates to monolithic ceramic capacitors suitable for miniaturization and achievement of large capacitance. In particular, the present invention relates to a monolithic ceramic capacitor comprising a ceramic sintered compact having a core-shell structure.
2. Description of the Related Art
Monolithic ceramic capacitors comprising sintered compacts having core-shell structures using barium-titanate-based ferroelectric materials are known. In a ceramic sintered compact having a core-shell structure, a core particle composed of barium-titanate-based ferroelectric ceramic is surrounded by a shell layer composed of a dielectric material having a dielectric constant which is lower than that of the barium titanate. In the production of the ceramic sintered compact having the core-shell structure, ceramic core materials such as TiO.sub.3 and BaCO.sub.3 in a given formulation are mixed and calcined. The calcined mixture is pulverized. The resulting powder is mixed with materials for forming a shell, e.g., an organic binder, a dispersant and water, to form a ceramic slurry. The ceramic slurry is shaped into a ceramic green sheet by, for example, a doctor blade process. On the ceramic green sheet, a conductive paste containing powdered metal, such as Ag, Ag--Pd, Ni or Cu is applied by printing to form internal electrodes.
Plural ceramic green sheets provided with internal electrodes are laminated together. The resulting laminate is pressed in the vertical direction (thickness direction) and is sintered. External electrodes are formed on the two ends of the resulting sintered compact to form a monolithic ceramic capacitor composed of a ceramic sintered compact having a core-shell structure.
The monolithic ceramic capacitor having such a core-shell structure is said to have satisfactory temperature characteristics.
Recently, monolithic ceramic capacitors are required to be further miniaturized and have higher capacitance. In barium-titanate-based monolithic ceramic capacitors having core-shell structures, however, dielectric constants have not been improved as expected. Thus, further miniaturization and higher capacitance in the barium-titanate-based monolithic ceramic capacitors pose significant problems.